Solvent extraction with a sultone solvent

ABSTRACT

A PROCESS FOR THE SELECTIVE EXTRACTION OF AROMATIC HYDROCARBNS FROM A FEED STOCK CONTAINING BOTH AROMATIC AND SATURATED HYDROCARBONS. THE PROCESS EMPLOYS A SOLVENT WHICH SELECTIVELY EXTRACTS AROMATIC HYDROCARBONS WITH RESPECT TO SATURATED HYDROCARBONS FROM A FEED STREAM. THE SOLVENT IS REMOVED FROM A MIXTURE OF SOLVENT AND FEED STOCK AND TREATED TO RECOVER A CONCENTRATED STREAM OF AROMATIC HYDROCARBONS.

United States Patent 3,723,303 SOLVENT EXTRACTION WITH A SULTONE SOLVENTStephen N. Massie, Palatine, and George E. Illingworth,

Arlington Heights, Ill., assignors to Universal Oil Products Company,Des Plaines, Ill.

No Drawing. Filed Mar. 22, 1971, Ser. No. 127,027

Int. Cl. Cg 21/16 U.S. Cl. 208325 11 Claims ABSTRACT OF THE DISCLOSURE Aprocess for the selective extraction of aromatic hydrocarbons from afeed stock containing both aromatic and saturated hydrocarbons. Theprocess employs a solvent which selectively extracts aromatichydrocarbons with respect to saturated hydrocarbons from a feed stream.The solvent is removed from a mixture of solvent and feed stock andtreated to recover a concentrated stream of aromatic hydrocarbons.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to a solvent extraction process. More specifically, the presentinvention relates to a process in which a sultone type compound isutilized, as a solvent, to selectively remove aromatic hydrocarbons froma feed stock containing both aromatic and saturated hydrocarbons.

Description of the prior art The solvent extraction of aromatichydrocarbons is well known in the art. Specifically, solvent extractionutilizing glycol and sulfolane type compounds as solvents to selectivelyremove aromatic hydrocarbons from mixture of saturated and aromatichydrocarbons are well known in the art. There is a multitude of issuedpatents relating to processes utilizing these and derivative compounds.The art, however, has not recognized the use of sultone type compoundsas solvents to selectively remove aromatic hydrocarbons from the mixtureof aromatic and saturated hydrocarbons.

SUMMARY OF THE INVENTION It is an object of this invention to provide asolvent extraction process to concentrate aromatic hydrocarbons from afeed stock containing them. It is another object of this invention toprovide a solvent extraction process utilizing a sultone type compoundas a selective solvent to remove aromatic hydrocarbons from a feed stockcontaining both aromatic and saturate hydrocarbons.

In terms of utility, the present process offers a process for theconcentration of valuable aromatic type hydrocarbons which can beutilized in a multitude of operations varying from gasoline produtcionto the production of plastics. Aromatics most readily separableutilizing the process of this invention include benzene, toluene or thexylenes. The saturated hydrocarbons in admixture with the aromaticsgenerally comprise cyclo-paraffins or the branched or straight chainparaflins boiling substantially the same temperature range as thearomatic compounds described above.

Feeds stocks which can be used in the process of this invention includethose derived from various crude fractions including straight rungasoline, reformed hydrocarbons or some of the products of catalyticcracking or hydrocracking reactions. Specific components included asfeed stocks are the aromatics such as benzene, toluene, ethylbenzene,para-xylene, meta-xylene, ortho-xylene, isopropylbenzene, thediethylbenzene, the triethylbenzenes, the methylethylbenzenes, or someother higher boiling aromatic compounds not specifically mentioned. Thesaturated hydrocarbons included-in the feed stock are parafiins andcyclo-paratfins. Specifically, branched or straight chain parafiinswhich can be in the feed stocks are those having from 7 to and including10 or more carbon atoms per molecule. In many instances they may have upto as many as 15 to 20 carbon atoms per molecule. Specific chainedparatfins include branched or straight chain pentanes, hexanes,heptanes, octane, nonane, etc. Typical of the cycloparafiins which canbe found in the feed stocks are some of the cyclopentanes, cyclohexane,and the alkyl derivatives thereof. Higher boiling cycloparaiiins whichalso can be included in the feed stocks include thedecahydronaphthalenes and bicyclo-parafiins.

Solvents which can be used in the process of this invention are chosenfrom the general class of compounds referred to as sultones. Sultonesare described as heterocyclic compounds which contain carbon, sulfur andoxygen atoms in a configuration generally described in the structure asdescribed below:

Wherein various substitutions which can be included at the Rsubstitutional groups above include of hydrogen, methyl, or ethylradical groups at any or all of the substitutional groups and n is aninteger of one to three. Utilizing the above formula, the followingmaterial can be utilized as solvent: 1,3-propane sultone, 1,3-butanesultone, 1,4-butane sultone, 2,4-butane sultone, 1,3-pentane sultone,2,4-pentane sultone, 3,5-pentane sultone etc. Other combinations may beincluded such as materials which contain methyl or ethyl groups on theend or in the middle of the chain of the above described formula. Inparticular, 1,3-propane sultone can be produced by the reaction ofsulfur trioxide and allyl alcohol followed by dehydration.

The sultones may be utilized in relatively pure forms or in mixtureswith Water and/or other organic compounds including sulfolane typecompounds or the ethylene glycols including diand tri-ethylene glycolsolvents. It has been found in extraction processing that smallquantities of the above substances can, in many instances, enhance theseparation abilities of an extract for various feed components. Inpatricular, aromatic components in admixture with saturate components ina feed stock can be made easier to separate.

Extraction conditions include liquid phase operations with sufficientpressure to maintain such operations. Temperatures can include thosefrom about ambient up to about 200 C. and in many instances up to about250 C. The higher temperature limitation may, in some instance, berequired to be lower than that stated where solvent easily decomposes atthe temperature proposed. The percentage of water or organic materialswhich can be present along with the solvent during extraction operationscan vary anywhere from a few percent up to as many as 10 or more weightpercent.

It is contemplated that in normal operations the solvent material willcontact the feed stock under extraction conditions in any one of anumber of contacting devices which are known to the art. Contactingdevices which can be utilized include the countercurrent flow, rotatingdisc contacters to allow an intimate mixing of feed and solventmaterials. It is contemplated that both the extract phase and rafiinatephase material can be removed from an extraction device and passed intovarious separation or treating means in order to eliminate solvent carryover by the raffinate stream and to allow separation of aromatics fromthe sultone solvent. Typically, the ratfinate material can be passedinto a water contacting device in which water can contact the raffinatematerial to wash any solvent carried out of the process by the raffinatestream. The extract phase material can generally be passed into anextractive distillation column in 5 which the more volatile component ofthe aromatic and solvent mixture passes overhead while the higherboiling fraction is removed from the bottoms fraction. In some instancesin which higher molecular weight aromatics are extracted, the solventmay instead pass overhead With the aromatics recovered in the bottomfraction. Some extract phase separation operations include an extractivedistillation column in series with a fractionating column in which theextractive distillation column gives a first separation of aromatics andsolvent with the fractionating column allowing a more completeseparation to take place. In cases where an organic compound or water isused in admixture with a solvent, it may be required to treat thesolvent with this substance in order to maintain a given concentrationof this substance in the solvent before the solvent is recycled into thecontacting zone. In other instances the solvent may be required to bepartially regenerated or treated in order to eliminate the contaminantsabsorbed within it before it is returned to the contactor.

EXAMPLES In this example a sultone material was used to illustrate aspecific embodiment of the process of this invention. The apparatus usedconsisted of a sealed bomb which could sustain a moderate amount ofpressure and temperatures up to about 200 C. The bomb was filled with apredetermined quantity of feedstock and the desired solvent and thenshaken to cause intimate mixing of both the feed and solvent materials.The bomb was then placed in a constant temperature bath maintained at121 C. with occasional agitation. After about one hour at 121 C. thecontents of the bomb were sampled by drawing off substantially all ofthe upper raffinate and lower extract phases. The results of theexperiment are shown in the table below:

EXTRACTION RESULTS USING iii-PROPANE SULTONE AS A SOLVENT Materialdescription Wt., grns. Wt. percent Feedstock:

Benzene 5.41 21.6 l\Iethylcyleopentane- 19. 6-1 78. 4

Total 25.05 100.0

Solvent:

1,3 propanesultone 48.42 97.5 Water 1. 22 2. 5

Total 40. 64 100.0

Railinate phase (upper layer):

1,3 propane sultone 0.21 1. 8

Benzene (Bz) Methyleyclopentane (MCP) Total Weight ratio Bz/MCP 0.18

Extract phase (lower layer)- 1,3 propane sultone- 38. 52 94. 1Benzene 1. 41 3. 5 58. 7 lt letliylcyelopentanen 1.00 2. 4 41. 3

Total 40. 93 100. 0 100.0

Weight ratio Bz/MCP 1. 41 Selectivity 7.82

rafiinate phases respectively. As can be seen in the table above, thematerial tested as a solvent was able to selectively concentratearomatic hydrocarbons in the extract or solvent phase.

The above example is offered as a specific embodiment of the process ofthis invention and is not to be taken as an undue limitation of thescope of the attached claims.

EMBODIMENT A broad embodiment of this invention resides in a process forseparating aromatic hydrocarbons from a feed mixture containing botharomatic and saturate hydrocarbons by contacting said feed mixtures witha solvent comprising a sultone, selectively extracting said aromaticsfrom said feed by said solvent and recovering aromatics from saidsolvent.

A more specific embodiment of this invention resides in a process forthe selective extraction of an aromatic hydrocarbon from a feedstockcontaining aromatic and saturate hydrocarbons which process comprisescontacting said feedstock with a solvent comprising a material havingthe formula:

or 3, and the R substitutions are selected from the group consisting ofhydrogen, methyl and ethyl radicals or combination thereof, at solventextraction conditions to effect the selective retention of aromatichydrocarbons by said solvent as compared to said saturate hydrocarbons,recovering solvent and said selectively retained aromatics andrecovering said selectively retained aromatics from said solvent.

We claim as our invention:

1. A process for the selective extraction of an aromatic hydrocarbonfrom a feed stock containing aromatic and saturated hydrocarbons whichprocess comprises contacting said feed stock with a solvent comprising amaterial having the formula:

wherein 12:1, 2

wherein each R substitution is selected from the group connsisting ofhydrogen, methyl and ethyl radicals and n is an integer from 3 to 5, atsolvent extraction conditions to effect the selective retention ofaromatic hydrocarbons by said solvent as compared to said saturatedhydrocarbons recovering solvent and said selectively retained aromaticsand recovering said selectively retained aromatics from said solvent.

2. Claim 1 further characterized in that said aromatic hydrocarbon isselected from the group consisting of benzene, toluene, xylene andethylbenzene.

3. Claim 2 further characterized in that said saturated hydrocarbon isselected from the group consisting of paraffins and cycloparaffins.

4. Claim 3 further characterized in that n is 3.

5. Claim 3 further characterized in that n is 4.

6. Claim 3 further characterized in that n is 5.

7. A process for the selective extraction of an aromatic hydrocarbonfrom a feed stock containing aromatic and saturated hydrocarbons, whichprocess comprises contacting said feed stock with a solvent comprising amaterial having the formula:

wherein each R substitution is selected from the group consisting ofhydrogen, methyl and ethyl radicals, at solvent extraction conditions toeffect the selective retention of aromatic hydrocarbons by said solventas compared to said saturated hydrocarbons, recovering solvent and saidselectively retained aromatics and recovering said selectively retainedaromatics from said solvent.

8. Claim 7 further characterized in that said aromatic hydrocarbonscontain from 6 to about 15 carbon atoms per molecule.

9. Claim 7 further characterized in that said saturated hydrocarbons areparafi'lnic hydrocarbons having from 6 to about 20 carbon atoms permolecule.

10. Claim 7 further characterized in that said saturated hydrocarbonsare cycloparaffins.

11. Claim 7 further characterized in that each R substitution ishydrogen.

References Cited UNITED STATES PATENTS 2,365,898 12/ 1944 Morris et a1.208-325 2,906,707 9/1959 Pollitzer 208-325 3,422,163 I/ 1969 Asselin208325 10 HERBERT LEVINE, Primary Examiner US. Cl. X.R. 260-674 SE

